The use of musculoskeletal allograft tissue in reconstructive orthopedic procedures and other medical procedures has markedly increased over the last decade. The most common allograft is bone. However, tendons, skin, heart valves and corneas are other common types of tissue allografts.
Prior to use, the allograft tissue must be evaluated for microbial contamination. The allograft product must be tested for bacterial contamination prior to release of the tissue for transplantation. Swabs are widely used in the pharmaceutical and medical device industry for evaluating microbial contaminants on small, hard, non-porous manufacturing equipment, in addition to detecting microbial contaminants in environmental monitoring programs. Some areas of the allograft are simply inaccessible to a swab, thereby not allowing for complete analysis of the allograft for microbial contaminants.
Another method used for detecting microbial contamination on allografts is destructive testing. Destructive testing using companion tissues (small sections of typically lower quality or unusable portions of the allograft) is routinely used to assess microbial contamination on entire allograft lots. This practice has come under intense scrutiny by regulatory agencies since the companion tissue may not be representative of the microbial contamination on entire allograft lot. Furthermore, the geometry of the companion tissue does not adequately represent the geometry of the entire allograft lot.
Recently, non-allograft materials from varying sources (bovine, ceramic, synthetic, etc.) have been used as a representative model of what the allograft tissue products are exposed to during handling and processing. The limitation with these materials is that they are not truly representative of the actual allograft. Furthermore, it is extremely difficult to fabricate synthetic samples to model every product category currently utilized for transplantation.
Prior to use, the allograft tissue must be treated with various agents in order to substantially eliminate microbial contamination as well as clean the tissue of residual blood constituents, bone marrow, residual connective tissue and gross musculature. A variety of cleaning processes have been developed in order to remove contaminants from the allograft and to inactivate microbial contaminants remaining on the allografts. However, these cleaning and inactivation methods are laborious and tedious, and often do not provide a high level of assurance that the allografts have been sufficiently cleaned (e.g., low or inconsistent log reductions in microbial contamination). In particular, many existing allograft cleaning processes require considerable manipulation of the allografts between steps, thus increasing the possibility of environmental cross-contamination. Existing processes also tend to be hard to regulate and control, and their efficacy can be technician dependent. Existing processes also tend to have a shielding or layering effect that can greatly reduce ultrasonic energy penetration and thus not clean as effectively. Furthermore, the shielding effect will also impede the liberation of contaminant microorganisms off of the tissues and into solution where they are more readily eradicated.
Following treatment, allograft products must be tested for bacterial contamination prior to release of the tissue for transplantation. Existing methods of assessing microbial contamination, however, suffer form the same limitations described above (e.g. considerable manipulation between steps, possibility for environmental cross-contamination, hard to regulate and control, technician dependent, etc.).
In the past, ultrasound has been utilized to reduce and/or eliminate microbial contamination of allograft products. Ultrasound is microbiostatic to most microbes, and is used primarily to reduce microbial loads from inanimate objects with specific bactericidal activity on gram-negative bacteria.
With the increased use of allograft products, there is a need to provide improved methods and apparatus for treating allografts in order to help provide the cleanest and safest allografts as well as confirm that the allografts are free from bacterial contamination.